Hi! I've had some experience with their fifth gen hobby laser. We got one at the lab I set up last year at the High School for Community Leadership. I ended up using the exhaust system that FSL sells with. I installed metal duct to the nearest window and built a panel from plexi bought at the mega-hardware depot down the street. We even used the laser to cut the plexi (though that's the only plexi I would cut without a proper filtration system).
I think that so long as you're cutting cardboard or card stock and your exhaust isn't at ground level, you'll probably be ok without a high-cost filtration system. If cutting plexi, aluminum, or other toxic nasties, it's best (and legally obligatory) to get a fume extractor (a la BOFA).
I'm a fan of the FSL Hobby Laser. In fact, I'm getting another for the lab at the school I started at this year. The only bummer is that it's water-cooled. And it takes a bit to get used to aligning the laser - but well worth sinking time into learning. Once the laser is aligned and focused properly, it plenty powerful for high school applications.
Jonathan Rothman
Teacher - Math, Technology & Design
Academy for Software Engineering